There's the tangible effect most homeowners fear: Property values of the occupied homes next door can drop as much as 2 percent a year. And there's the ripple effect: Cable, phone and power companies see a dip in revenue. Retailers see fewer customers at existing stores and are less likely to open new ones. Code enforcement calls go up, putting a strain on cities already hurt by budget cuts.

Because of the ongoing foreclosure and credit crisis, there are more vacant homes in America now than ever before. Although the evidence is largely anecdotal, some estimate as many as 7 percent of the houses in the bay area are vacant.

The Center for Responsible Lending estimates that homes left vacant by foreclosure have decreased property values a total of $202-billion nationwide, and that homeowners living near vacant homes see their property values drop an average of $5,000.

And it's expected to get worse. The center projected that 2.25-million Americans would lose their homes to foreclosure in 2008-09, and of those, about 195,000 would be in Florida.

More proof of the rise in vacant homes comes from the U.S. Census Bureau, which reports that the number of vacant homes for sale in the United States inched up to 2.3-million in the first quarter of this year, the highest level ever measured. The percentage of homes that are vacant and for sale also has been rising, from a low of 1.5 percent in 2001 to 2.9 percent in the first quarter.

The precise number of vacant homes in the Tampa Bay area is difficult to track because properties fall in and out of the category every day. But there are definite clues.

Deborah Farmer, president of the Greater Tampa Association of Realtors, said she notices the spike in vacant homes firsthand. "Over half of the homes I show now are vacant," Farmer said, "and I bet that number is much the same throughout the area."

Farmer and others also say that what was once an urban problem has spread to the suburbs.

Bright House spokesman Joe Durkin said that while cable features such as movies on demand have grown dramatically, as much as 7 percent of homes in the Tampa Bay area are vacant, and new customer growth is flat.

Beside keeping a lid on new cable customers, both Progress Energy and Tampa Electric have seen an increase in "low usage" accounts, a sign that a property is vacant. In July 2005, 4.2 percent of Progress Energy's customers fell into that category. This July, the share climbed to 5.4 percent.

Another sign is the low number of new customers. Tampa Electric recorded just 0.2 percent growth in the second quarter, down from a decade average of 2.5 percent. In the 12 months ending June 30, Progress Energy added just 2,000 customers, down 93 percent from the 29,000 added the year before.

"No one really knows for sure how many (vacant houses) are out there," said Joseph Schilling, a professor at Virginia Tech's Metropolitan Institute and co-founder of the National Vacant Properties Campaign, which helps cities tackle housing problems. "The best way to find out is to get community organizations together and walk the streets."

One thing Schilling is certain of is the severity of the crisis.

"A number of properties that would normally be vacant three to five months are now vacant 12 to 18 months or longer," he said. "And the longer they're vacant, the more susceptible they are to vandalism and abandonment.

"We're at the very beginning of the housing crisis," he added. "We'll be dealing with a lot more properties that are dilapidated and abandoned."

Todd Yost already is.

"We have noticed an increase in complaints about vacant and boarded properties," said Yost, St. Petersburg's code compliance director.

Yost's office is charged with responding to complaints, giving the owner time to respond and then making sure the work is done. If not, the boarding of windows, repairing of pool fences or yard clearing is done by contractors and the property owner is billed for the work.

After a four-year decline, the number of vacant and boarded structures in St. Petersburg has risen from 262 in 2006 to 318 through April 1 of this year. And Yost's budget has been cut by 25 percent.

"We are not much different than what's going on in the rest of the area," he said.

Most owners usually try to explain why a home has fallen into disrepair. Many, Yost said, say they don't have jobs and can't afford to take care of a house facing foreclosure.

"If it's an aesthetic thing," he said, "the (code enforcement) board may give them more time.

"I think everybody is pretty susceptible to the economic challenges out there today."

Staff writer Asjylyn Loder contributed to this report. Tom Zucco can be reached at zucco@sptimes.com or (727) 893-8247.

County

Projected number of homes lost through foreclosure on 2005-06 subprime loans

Number of houses losing value due to nearby subprime foreclosures

Average decrease in house value

Decline in county's house values and tax base from subprime foreclosures (2005-06 loans)